Fiber optic couplers are used as optical beam splitters between two or more fibers. Fused biconical tapered couplers are formed generally by placing two bare single mode fibers in contact with each other, adding tension to the fibers, and heating the fibers using a heat source, for example a flame. As the fibers soften, they fuse together to form the fused biconical tapered coupler.
The conventional manufacture of fiber optic devices such as the fused biconical tapered coupler suffer from the fundamental problem that manual handling by technicians or operators introduces variations to the manufacturing process. Depending on the fiber optic device being formed, a considerable amount of error may be introduced by the handling of an optical fiber by an operator or technician. For example, conventional formation of a coupler includes removing of an outer coating from two or more optical fibers and placing the exposed optical fibers in contact with each other. The fibers may be twisted together, depending on the particular technique used to manufacture the coupler. The fibers are then fused together by heat, as the fibers are placed under tension by slowly and carefully pulling them apart at a predetermined rate. Given the delicate nature of optical fibers, the manufacture of optical fiber couplers requires highly skilled and trained technicians.
An additional problem with conventional manufacturing techniques is that the optical characteristics of the fiber optic devices during manufacture are uncontrollable. Skilled technicians with experience from trial and error have been needed to anticipate the optical characteristics of a fiber optic device during manufacture. For example, technicians making fused biconical tapered couplers would recognize that a jump in the detected coupling ratio occurs when a heat source is suddenly removed from the heated optical fibers. Technicians would attempt to anticipate the jump in the detected coupling ratio such that the heat source, when removed, would cause the detected coupling ratio to jump to the desired level. Hence, the yield of the manufacturing process would be unpredictable and entirely dependent on the individual technician's expertise.
U.S. Pat. No. 5,386,490 to Pen et al., incorporated in its entirety herein by reference, discloses a workstation for manufacturing a coupler between at least two optical fibers. A technician threads an optical fiber from an optical fiber spool into the clamping assembly. The technician is also needed to terminate the bare fiber into a bare fiber adaptor, used to hold the end of the optical fiber relative to a photodiode. Hence, the arrangement disclosed by Pen et al. still requires an operator to thread the optical fiber from a spool to the clamping assembly and mount the end of the optical fiber into a termination point. Further, operator intervention is still required for subsequent manufacturing operations, including hermetic sealing, testing, and packaging. Consequently, variations due to operator handling still exist.
Hence, the conventional manufacturing process suffers an inherent degree of variability due to manual handling by the skilled technicians. In addition, the necessity of skilled technicians greatly increases the manufacturing costs for the fiber optic devices. Finally, use of skilled technicians limits the production capacity, since technicians are subject to fatigue.